OBJECTIVETo evaluate the capillary isoelectric focusing (CIEF) method for the estimation of blood hemoglobin A2 (Hb A2) concentrations in routine thalassemia screening.

METHODSA total of 105 samples from healthy adults and 93 samples with positive phenotypes were collected by routine thalassemia screening. CIEF was compared with Helena spife combo electrophoresis system for Hb A2 measurement and its precision and reproducibility were tested by analyzing intra-assay or inter-assay coefficient of variations(CVs). The reliability and veracity of Hb A2 measurement by CIEF for the detection of alpha- and beta- thalassemia including Hb E were evaluated by genotyping of 93 consecutive samples for routine thalassemia screening.

RESULTSBy us e of CIEF for measurement of Hb A2 in a local healthy adult population, the range of reference value(3.59%-5.23%) was obtained. The results of CIEF showed good linearity relation to that of conventional Hb electrophoresis assay. All thalassemia carriers (43 cases of alpha-thals and 44 of beta-thals) or Hb E carriers (6 cases) presumptively identified by the present CIEF for the quantification of Hb A2, combined with routine RBC parameters for indicating microcytosis and hypochromia were confirmed to be the heterozygous or compound heterozygous defects of alpha- or beta- globin gene by molecular diagnosis, without any false positive or false negative results.

CONCLUSIONThe measurement of Hb A2 by CIEF method is rapid, precise and reproducible; it could be used in routine screening for alpha- or beta- thalassemia.